The invention relates to a transaction system based on machine-based speech recognition, comprising a speech input, speech recognition means fed by said speech input, dialogue control means fed by said speech recognition means, and speech generation means fed by said dialogue control means for outputting question statements and verifier statements from a statement repertoire set, and for executing a human-machine dialogue with said system, until said dialogue control means has recognized a viable transaction formulation comprising a plurality of user-provided slot fillers for specifying said transaction. By way of example, the transaction may relate to a financial transaction, to an enquiry system such as pertaining to a trains timetable or a telephone directory, or to a ticket or other commodity ordering service. Depending on the envisaged reliability level, the correspondence between what the user person wishes to convey, and the understanding thereof by the machine, must concord to certain often high levels of confidence. First, the message comprises so-called slot filler items, that may represent numbers, locations, prices, clock times, dates, and various other, depending on the field of application, and which items represent the backbone of the message. The slot filler items must be recognized, both as to their content, and as to their context. Sometimes, the message may have more than one slot filler item for the same slot. The statements may be built from smaller units of speech such as words, so that the statements are stored indirectly, as it were.
As the case may be, the message may contain qualifiers, such as `not`, `or`, that can have a distinct influence on the meaning of associated slot filler items, and therefore, must be recognized as well. Finally, the user speech can comprise general items that have no relevance for the content of the message, but which may not be confused with the two earlier categories. Often, the user person cannot provide the message in the form of a single sentence; the message must then be extracted from the user in bits and pieces. Also, various problems can occur in the dialogue that must by necessity ensue.